relax SVN archive

Updated the version number to 3.1.1 on the webpage http://www.nmr-relax.com/api/.

Updated the HTML version of the relax manual to version 3.1.1.

This is for http://www.nmr-relax.com/manual/index.html.

Updated the http://www.nmr-relax.com/download.html webpage for relax version 3.1.1.

Added the relax 3.1.1 manual to the repository.

Updated the version number to relax 3.1.1.

Backported the relax 3.1.1 CHANGES file addition to trunk.

The command used was:
svn merge -r21934:21935 svn+ssh://bugman@.../svn/relax/tags/3.1.1 .

Updated the CHANGES file for relax version 3.1.1.

relax version 3.1.1.

This is a minor feature release which adds support the 'NS MMQ 3-site linear', 'NS MMQ 3-site',
'NS R1rho 3-site linear', and 'NS R1rho 3-site' relaxation dispersion models. There is also
improved support for R1rho data sets where multiple offsets and multiple spin-lock fields have been
collected for each spin.

Python 3 fixes for the relax_disp.r2eff_read_spin user function.

The check for the dispersion point column now only runs if that argument is set. In addition, the
offset column is now also being checked.

Removed a printout from the Relax_disp.test_r1rho_kjaergaard GUI test as this is fatal for Python 3.